diff --git a/audio/2.0/IPrimaryDevice.hal b/audio/2.0/IPrimaryDevice.hal
index 6beddfe..f1dd56e 100644
--- a/audio/2.0/IPrimaryDevice.hal
+++ b/audio/2.0/IPrimaryDevice.hal
@@ -76,7 +76,7 @@
      */
     setBtScoWidebandEnabled(bool enabled) generates (Result retval);
 
-    enum TtyMode {
+    enum TtyMode : int32_t {
         OFF,
         VCO,
         HCO,